Phytostimulating Activity of Methylobacterium dichloromethanicum subsp. dichloromethanicum DM4 and Its groEL2 Gene Knockout Mutant

For the first time, the genome of the dichloromethane destructor Methylobacterium dichloromethanicum subsp. dichloromethanicum DM4 was analyzed for the presence of genetic determinants indicating its potential as a plant growth stimulator, and the ability of this strain and its groEL2 gene mutant to improve plant growth was determined. The genome of strain DM4 contains genes involved in the biosynthesis of phytohormones (indolyl-3-acetic acid and cytokinins), siderophores, carotenoids, poly-β-hydroxybutyrate, hydrolytic enzymes, as well as enzymes involved in the degradation of D-cysteine, protection from UV-damage, and phosphate solubilization. Inoculation of lettuce sprouts by strain DM4 had a positive effect on plant growth and development and increased adaptive defense and resistance to short-term temperature stress in plant growth experiments. Comparative analysis of the production of auxins, siderophores, hydrolytic enzymes, D-cysteine desulfohydrase activity, and the ability to solubilize insoluble phosphates in strains DM4 and DM4 ΔgroEL2 showed that disruption of the groEL2 gene led to a decrease in the synthesis of indole derivatives and phosphate solubilizing ability in the mutant. Assessment of the impact of inoculation of lettuce plants by these strains also demonstrated a decrease in the phytostimulating potential of DM4 ΔgroEL2 compared to the original strain. The data obtained indicate that the chaperonin GroEL2 in M. dichloromethanicum subsp. dichloromethanicum DM4 indirectly affects its phytostimulating activity.